A flame-retardant polymer electrolyte for lithium-ion batteries and its preparation method and application
The molecular structure of polymer electrolyte is optimized through copolymerization modification technology, and the shortcomings of polymer electrolytes in flame retardant performance and ionic conductivity are solved, and high-efficiency flame retardant and high-conductivity polymer electrolytes are achieved, which improves the safety and stability of lithium batteries.
Patent Information
- Application Number
- CN202411864012.9
- Authority / Receiving Office
- CN · China
- Patent Type
- Patents(China)
- Current Assignee / Owner
- Filing Date
- 2024-12-18
- Publication Date
- 2025-09-05
- Estimated Expiration
- 2044-12-18
AI Technical Summary
The existing polymer electrolytes have shortcomings in flame retardant performance and ionic conductivity, especially in high temperature performance degradation problems, and the incompatibility of fillers with polymer matrix leads to interface separation, increasing battery internal resistance, and affecting battery performance.
By adopting copolymerization modification technology, the molecular structure of the polymer electrolyte is optimized by introducing appropriate functional groups and copolymerization methods to prepare polymer electrolytes with high efficiency flame retardant and conductivity, including the copolymerization process using materials such as acrylonitrile, vinyl acetate, bacterial cellulose and lithium bistrifluoromethanesulfonimide.
While ensuring the excellent flame retardant effect of polymer electrolyte, it significantly improves its ionic conductivity, improves the safety and cycle stability of lithium batteries, controls the combustion reaction of combustible materials, inhibits the growth of lithium dendrites, and improves the mechanical properties and thermal stability of the battery.
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Abstract
Description
Technical Field
[0001] The present invention relates to the technical field of flame-retardant polymer electrolytes, and in particular to a flame-retardant polymer electrolyte for lithium-ion batteries, a preparation method thereof, and applications thereof. Background Art
[0002] Since their introduction in the 1990s, lithium-ion batteries have been widely used in consumer electronics, electric vehicles, and energy storage systems due to their high energy density, long lifespan, and environmental friendliness. With growing market demand, especially for electric vehicles and portable electronics, which place higher demands on battery performance, further improving the safety, energy density, and cycling stability of lithium-ion batteries has become a hot topic of research. However, despite their important role in various fields, lithium-ion batteries remain a key factor hindering their widespread application. Liquid electrolytes are the core components of lithium-ion batteries. Traditional liquid electrolytes primarily consist of organic solvents and lithium salts. Commonly used organic solvents, such as carbonates and ethers, offer good solubility, but their volatility and flammability often lead to thermal runaway, especially under extreme conditions such as high temperature or short circuits. In severe cases, they can even cause battery fire or explosion, posing a significant threat to battery safety. Therefore, reducing the flammable components in batteries and improving their thermal stability have become urgent technical challenges.
[0003] In response to these safety issues, polymer electrolytes have recently attracted widespread attention as alternatives to liquid electrolytes. By replacing traditional liquid electrolytes with polymer electrolytes, polymer lithium batteries (LiBs) can effectively avoid the flammability and volatility issues associated with liquid electrolytes, thereby improving battery safety. The use of polymer electrolytes in LiBs can eliminate the safety risks associated with traditional liquid organic electrolytes. In particular, they can prevent electrolyte combustion in the event of thermal runaway or internal short circuits, significantly improving battery safety. However, widespread application of polymer electrolytes still faces numerous challenges. First, polymer electrolytes generally exhibit poor ionic conductivity. Because their ionic conduction mechanism differs from that of liquid electrolytes, the resistance at the solid-solid interface is high, resulting in high interfacial impedance between the electrode and the polymer electrolyte, resulting in low battery conductivity and limiting energy output and efficiency. Second, polymer electrolytes still lack mechanical strength and thermal stability. Especially at high temperatures, polymer electrolytes can decompose or become structurally unstable, impacting the long-term stability and safety of the battery. Therefore, improving the conductivity of polymer electrolytes while ensuring their safety and stability remains a major research topic.
[0004] Currently, researchers are attempting to improve the performance of polymer electrolytes through doping. Doping involves introducing fillers or dopants into polymer electrolytes in the hope of enhancing their ionic conductivity or improving their thermal stability. However, this approach often faces the problem of incompatibility between the filler and the polymer matrix, leading to interfacial separation of the polymer electrolyte, which in turn increases the battery's internal resistance and reduces performance.
[0005] Therefore, how to further improve the flame retardancy of polymer electrolytes without sacrificing conductivity has become a major technical challenge. Furthermore, existing research on the thermal stability and cycling performance of polymer electrolytes at high temperatures remains insufficient. In particular, performance degradation at high temperatures remains a significant issue in practical applications. Therefore, finding a technical solution that can enhance the ionic conductivity of polymer electrolytes while maintaining good thermal stability and flame retardancy is particularly urgent and necessary.
[0006] This invention aims to address the deficiencies of existing polymer electrolytes in terms of flame retardancy and ionic conductivity, providing a polymer electrolyte with highly effective flame retardancy and conductivity. By optimizing the polymer electrolyte's molecular structure through copolymerization and introducing appropriate functional groups, the invention effectively enhances the polymer electrolyte's ionic conductivity while maintaining its excellent flame retardancy, thereby improving the safety and cycling stability of lithium batteries. This technological innovation not only resolves the conflict between conductivity and flame retardancy in existing polymer electrolytes but also provides new ideas and solutions for promoting the practical application of polymer electrolytes. Summary of the Invention
[0007] In order to achieve the above-mentioned purpose of the invention, in view of the above-mentioned technical problems,
[0008] The present invention provides a flame retardant polymer electrolyte using copolymerization modification technology and a preparation method thereof, thereby preparing a polymer electrolyte with high efficiency flame retardancy and electrical conductivity.
[0009] The present invention provides a method for preparing a flame-retardant polymer electrolyte for lithium-ion batteries, characterized in that the preparation method comprises the following steps:
[0010] (1) dissolving acrylonitrile and vinyl acetate in deionized water to obtain solution A, and adding sodium lauryl sulfate and potassium persulfate to the solution A under a nitrogen atmosphere to obtain solution B;
[0011] (2) soaking the solution B in a diethylenetriamine solution to obtain a solution C;
[0012] (3) Filtering the solution C, washing, and drying to obtain product D;
[0013] (4) adding bacterial cellulose and lithium bis(trifluoromethanesulfonyl)imide to the product D, and dissolving the product D in N-methylpyrrolidone to obtain a solution E;
[0014] (5) pouring the solution E into a mold, heating and evaporating the solvent to obtain a flame retardant polymer electrolyte AP (AN-VAC),
[0015] Preferably, the specific process of step (1) corresponding to every 8-10 g of acrylonitrile is as follows: 8-10 g of acrylonitrile and 1-1.5 g of vinyl acetate are dissolved in 30-35 mL of deionized water to obtain solution A; 0.2-0.3 g of sodium lauryl sulfate and 0.3-0.4 g of potassium persulfate are slowly added to solution A under nitrogen conditions to obtain a homogeneous solution B.
[0016] Preferably, the specific steps of step (2) are: soaking the homogeneous solution B in 40-50 mL of diethylenetriamine solution under a nitrogen atmosphere to obtain solution C;
[0017] Preferably, the specific steps of step (3) are: filtering the solution C, washing it with deionized water and ethanol in sequence to obtain a white solid product; heating and drying the white solid product to obtain product D, and the heating temperature is 60-80°C.
[0018] Preferably, the specific steps of step (4) are: mixing 1-1.2 g of product D, 3-4 g of bacterial cellulose with a mass concentration of 0.4% and 0.3-0.32 g of lithium bis(trifluoromethanesulfonyl)imide, and dissolving them in 12-15 ml of N-methylpyrrolidone to obtain solution E.
[0019] Preferably, the solution E is poured onto a polytetrafluoroethylene template and heated at 60-80° C. for 5-7 h to obtain a flame retardant polymer electrolyte AP (AN-VAC).
[0020] Preferably, in step (1), the concentration of acrylonitrile is 95-99% w / v, and the concentration of vinyl acetate is 95-99% w / v; in step (2), the concentration of N-methylpyrrolidone is 95-99% w / v.
[0021] The present invention also provides a flame retardant polymer electrolyte for a lithium ion battery. The flame retardant polymer electrolyte is prepared by the above-mentioned preparation method.
[0022] The present invention also provides a method for preparing a flame retardant polymer electrolyte lithium ion battery, wherein the lithium battery comprises a lithium half cell or a lithium full cell.
[0023] The lithium half-cell preparation method comprises the following steps:
[0024] (A) Lithium iron phosphate: carbon black: polyvinylidene fluoride was dispersed in N-methylpyrrolidone in a ratio of 8:1:1, ground evenly, and then coated on aluminum foil with a scraper and dried to obtain a lithium iron phosphate electrode;
[0025] (B) A lithium battery was prepared using a metal lithium sheet as the negative electrode, a lithium iron phosphate sheet as the positive electrode, and AP (AN-VAC) as a polymer flame retardant electrolyte.
[0026] The lithium full battery preparation method comprises the following steps:
[0027] (a) Lithium iron phosphate: carbon black: polyvinylidene fluoride was dispersed in N-methylpyrrolidone in a ratio of 8:1:1, ground evenly, and then coated on aluminum foil with a scraper and dried to obtain a lithium iron phosphate electrode;
[0028] (b) artificial graphite: carbon black: polyvinylidene fluoride was dispersed in N-methylpyrrolidone in a ratio of 8:1:1, ground evenly, and then coated on aluminum foil using a scraper and dried to obtain a graphite electrode;
[0029] (c) A lithium battery was prepared using graphite as the negative electrode, lithium iron phosphate as the positive electrode, and AP (AN-VAC) as the polymer flame retardant electrolyte.
[0030] The AP (AN-VAC) is prepared by the above-mentioned preparation method.
[0031] The present invention also provides a flame-retardant polymer electrolyte lithium ion battery, which is prepared by the above-mentioned preparation method.
[0032] The beneficial effects brought about by the technical solution provided by the present invention are:
[0033] The present invention utilizes economical and practical PAN as the main material and synthesizes AP(AN-VAC) through copolymerization and modification to produce a polymer electrolyte AP(AN-VAC) with excellent flame retardancy. The copolymerization and modification technology not only enables AP(AN-VAC) to eliminate free radicals released by PAN combustion, but also enables the flame retardant effect to be effective even at high temperatures.
[0034] Secondly, AP (AN-VAC) can effectively improve the safety performance of polymer electrolytes through -NH2 under thermal runaway conditions, control the combustion reaction of combustibles, and at the same time promote the movement of polymer electrolyte matrix chains and the C=O functional groups as lithium ion migration sites to improve electron transfer and ion transport. It also improves the mechanical properties of the polymer by forming hydrogen bonds through its own functional groups, inhibits the growth of lithium dendrites, and thus improves the cycle performance of lithium batteries. BRIEF DESCRIPTION OF THE DRAWINGS
[0035] Figure 1 : Infrared image of AP(AN-VAC)1 obtained in Example 1;
[0036] Figure 2 : Scanning electron micrograph of AP(AN-VAC)1 obtained in Example 1;
[0037] Figure 3 : Thermogravimetric image of AP(AN-VAC)1 obtained in Example 1;
[0038] Figure 4 : Thermogravimetric diagram of PAN obtained in Comparative Example 1;
[0039] Figure 5 : Thermogravimetric diagram of P(AN-VAC) obtained in Comparative Example 2;
[0040] Figure 6 : Limiting oxygen index experimental diagram of Example 1 and control groups 1 and 2;
[0041] Figure 7 : Nyquist plot of the AP(AN-VAC)1 half-cell obtained in Example 1;
[0042] Figure 8 : Nyquist plot of the PAN half-cell obtained in Comparative Example 1;
[0043] Figure 9 : Nyquist plot of the P(AN-VAC) half-cell obtained in Comparative Example 2;
[0044] Figure 10 : Cycle-specific capacity diagram of the AP(AN-VAC)1 half-cell obtained in Example 1 at different rates;
[0045] Figure 11 : Cycle-specific capacity diagram of the PAN half-cell obtained in Comparative Example 1 at different rates;
[0046] Figure 12 : P (AN-VAC) half-cell obtained in Comparative Example 2 cycle at different rates - specific capacity diagram;
[0047] Figure 13 : Cycle-specific capacity diagram of the AP(AN-VAC)2 half-cell obtained in Example 2 at different rates;
[0048] Figure 14 : Cycle-specific capacity diagram of the AP(AN-VAC)5 half-cell obtained in Example 3 at different rates;
[0049] Figure 15: Cycle-specific capacity diagram of the AP(AN-VAC)9 half-cell obtained in Example 4 at different rates; DETAILED DESCRIPTION
[0050] In order to make the purpose, technical solutions and advantages of the present invention more clearly understood, the present invention will be further described in detail below in conjunction with the embodiments. Of course, the specific embodiments described herein are only used to explain the present invention and are not intended to limit the present invention.
[0051] Example 1: Changing the synthesis temperature of AP(AN-VAC)1 to 60°C
[0052] (1) Synthesis of AP(AN-VAC)1
[0053] In 60 o Synthesis of AP(AN-VAC)1 under C conditions
[0054] 1. Dissolve 9 g of acrylonitrile and 1 g of vinyl acetate in 30 mL of deionized water to obtain solution A. Slowly add 0.2 g of sodium lauryl sulfate and 0.3 g of potassium persulfate to solution A at room temperature to obtain a homogeneous solution B.
[0055] 2. The homogeneous solution B was immersed in 40 mL of diethylenetriamine solution under nitrogen atmosphere to obtain solution C; the solution C was filtered and washed with deionized water and ethanol in sequence to obtain a white solid product; the white solid product was heated for 60 o After drying C, product D was obtained.
[0056] (2) Preparation of organic polymer electrolytes
[0057] 1. Mix 1 g of product D, 3 g of 0.4% bacterial cellulose, and 0.3 g of lithium bis(trifluoromethanesulfonyl)imide, and dissolve in 15 ml of N-methylpyrrolidone (NMP) to obtain solution E.
[0058] The solution E was poured onto a polytetrafluoroethylene template, 60 o C for 6 h to obtain the flame-retardant polymer electrolyte AP(AN-VAC)1;
[0059] The concentration of acrylonitrile is 95% w / v, the concentration of vinyl acetate is 95% w / v, and the concentration of N-methylpyrrolidone is 95% w / v;
[0060] 2. The flame-retardant polymer electrolyte AP(AN-VAC)1 was prepared into a disc with a diameter of 16 mm;
[0061] (3) Preparation of positive electrode: Disperse lithium iron phosphate (LFP): carbon black: PVDF = 8:1:1 with N-methylpyrrolidone, grind evenly, apply it on aluminum foil with a scraper, and dry to obtain lithium iron phosphate electrode;
[0062] (4) Preparation of lithium half-cell: Use lithium metal sheet as negative electrode, lithium iron phosphate electrode as positive electrode, and AP(AN-VAC)1 as polymer electrolyte to prepare 2032 button cell;
[0063] The graphite used is: CLUDE, artificial graphite powder SAG20N for lithium batteries;
[0064] The carbon black used is: CLUDE, conductive silicate carbon black for lithium battery positive electrode.
[0065] Example 2: Changing the AP (AN-VAC) synthesis temperature to 70°C
[0066] (1) Synthesis of AP(AN-VAC)2
[0067] Synthesis of AP(AN-VAC)2 at 70 ℃
[0068] 1. Dissolve 9 g of acrylonitrile and 1 g of vinyl acetate in 30 mL of deionized water to obtain solution A. Slowly add 0.2 g of sodium lauryl sulfate and 0.3 g of potassium persulfate to solution A at room temperature to obtain a homogeneous solution B.
[0069] 2. The homogeneous solution B was immersed in 40 mL of diethylenetriamine solution under nitrogen atmosphere to obtain solution C; the solution C was filtered and washed with deionized water and ethanol in sequence to obtain a white solid product; the white solid product was heated at 70 o After drying C, product D was obtained.
[0070] (2) Preparation of organic polymer electrolytes
[0071] 1. Mix 1 g of product D, 3 g of 0.4% bacterial cellulose, and 0.3 g of lithium bis(trifluoromethanesulfonyl)imide, and dissolve in 15 ml of N-methylpyrrolidone (NMP) to obtain solution E.
[0072] The solution E was poured onto a polytetrafluoroethylene template, 70 o C for 6 h to obtain the flame-retardant polymer electrolyte AP (AN-VAC);
[0073] The concentration of acrylonitrile is 95% w / v, the concentration of vinyl acetate is 95% w / v, and the concentration of N-methylpyrrolidone is 95% w / v;
[0074] 2. The flame-retardant polymer electrolyte AP(AN-VAC)2 was prepared into a disc with a diameter of 16 mm;
[0075] (3) Preparation of positive electrode: Disperse lithium iron phosphate (LFP): carbon black: PVDF = 8:1:1 with N-methylpyrrolidone, grind evenly, apply it on aluminum foil with a scraper, and dry to obtain lithium iron phosphate electrode;
[0076] (4) Preparation of lithium half-cell: Use lithium metal sheet as negative electrode, lithium iron phosphate electrode as positive electrode, and AP(AN-VAC)2 as polymer electrolyte to prepare 2032 button cell;
[0077] The graphite used is: CLUDE, artificial graphite powder SAG20N for lithium batteries;
[0078] The carbon black used is: CLUDE, conductive silicate carbon black for lithium battery positive electrode.
[0079] Example 3:
[0080] The preparation process is similar to that of Example 1, except that, in the preparation process of the organic polymer electrolyte, in step 1, 4 g of bacterial cellulose is added to synthesize AP(AN-VAC)5.
[0081] Example 4:
[0082] (1) Synthesis of AP(AN-VAC)
[0083] Synthesis of AP(AN-VAC)9 at 60 ℃
[0084] 1. Dissolve 10 g acrylonitrile and 1.5 g vinyl acetate in 35 mL deionized water to obtain solution A. Slowly add 0.3 g sodium lauryl sulfate and 0.4 g potassium persulfate to solution A at room temperature to obtain a homogeneous solution B.
[0085] 2. The homogeneous solution B was immersed in 50 mL of diethylenetriamine solution under a nitrogen atmosphere to obtain solution C. Solution C was filtered and washed with deionized water and ethanol in sequence to obtain a white solid product. The white solid product was heated at 60°C and dried to obtain product D.
[0086] (2) Preparation of organic polymer electrolytes
[0087] 1. Mix 1.2 g of product D, 4 g of 0.4% bacterial cellulose, and 0.32 g of lithium bis(trifluoromethanesulfonyl)imide, and dissolve in 15 ml of N-methylpyrrolidone (NMP) to obtain solution E.
[0088] The solution E was poured onto a polytetrafluoroethylene template and heated at 60° C. for 7 h to obtain a flame retardant polymer electrolyte AP(AN-VAC)9;
[0089] The concentration of acrylonitrile is 99% w / v, the concentration of vinyl acetate is 99% w / v, and the concentration of N-methylpyrrolidone is 99% w / v;
[0090] 2. The flame-retardant polymer electrolyte AP(AN-VAC)9 was prepared into a disc with a diameter of 16 mm;
[0091] (3) Preparation of positive electrode: Disperse lithium iron phosphate (LFP): carbon black: PVDF = 8:1:1 with N-methylpyrrolidone, grind evenly, apply it on aluminum foil with a scraper, and dry to obtain lithium iron phosphate electrode;
[0092] (4) Preparation of lithium half-cell: Use lithium metal sheet as negative electrode, lithium iron phosphate electrode as positive electrode, and AP (AN-VAC) 9 as polymer electrolyte to prepare 2032 button cell;
[0093] The graphite used is: CLUDE, artificial graphite powder SAG20N for lithium batteries;
[0094] The carbon black used is: CLUDE, conductive silicate carbon black for lithium battery positive electrode.
[0095] Comparative Example 1
[0096] The preparation method is the same as that in Example 1, except that PAN is used to replace the membrane formed by product D, the PAN membrane is prepared according to the method of step (2) of Example 1, the PAN membrane is used as the polymer electrolyte, and the 2032 button battery is prepared according to the method of steps (3)-(4) of Example 1.
[0097] Comparative Example 2
[0098] The preparation method is the same as that in Example 1, except that no diethylenetriamine solution is added for copolymerization modification in step (1), and the P(AN-VAC) membrane is prepared according to the method of step (2) of Example 1. The P(AN-VAC) membrane is used as the polymer electrolyte, and the 2032 button battery is prepared according to the method of steps (3)-(4) of Example 1.
[0099] Experimental testing of Example 1 and Comparative Examples 1 and 2:
[0100] 1. Use Fourier transform infrared spectrometer to detect the functional groups of AP(AN-VAC)1 Figure 1 shown.
[0101] from Figure 1It can be seen that AP(AN-VAC)1 was successfully synthesized with a unique absorption peak at 3200.
[0102] 2. The morphology of AP(AN-VAC)1 detected by scanning electron microscopy is as follows Figure 2 shown.
[0103] from Figure 2 It can be seen that the film is formed by heat, and the surface of the film is very uniform with few pores, which is conducive to close contact with the lithium negative electrode.
[0104] 3. Thermogravimetric test results of AP(AN-VAC)1 membrane under nitrogen conditions are as follows Figure 3 shown.
[0105] from Figure 3 It can be seen that the effect of AP(AN-VAC)1 membrane is very good and it still maintains 50% at high temperature, but the decomposition temperature of AP(AN-VAC)1 membrane is higher, which proves that it has better thermal stability.
[0106] 4. Thermogravimetric test results of PAN membrane under nitrogen conditions are as follows Figure 4 As shown. Figure 4 It can be seen that the PAN film only maintains 43% under high temperature conditions.
[0107] 5. Thermogravimetric test results of P(AN-VAC) membrane under nitrogen conditions are as follows Figure 5 As shown. Figure 5 It can be seen that the P(AN-VAC) membrane maintains 41%, and the decomposition temperature of the P(AN-VAC) membrane is not as high as that of the AP(AN-VAC)1 membrane.
[0108] 6. The flame retardant performance test results of AP (AN-VAC) 1 film are as follows Figure 6 shown.
[0109] Figure 6 is the limiting oxygen index test result, from Figure 6 As can be seen from the figure, the limiting oxygen index of AP(AN-VAC)1 is 24%, which once again proves that the copolymerization reaction inhibits the combustion of the film.
[0110] 7. The battery performance test results of the AP(AN-VAC)1 membrane prepared in Example 1 and the PAN membrane and P(AN-VAC) membrane of the control group are shown as follows: Figure 7-9 shown.
[0111] AP(AN-VAC)1 film, PAN film and P(AN-VAC) film were used to assemble lithium half-cells and Nyquist tests were performed. The results are shown in Figure 2. Figure 7-9 As shown, from Figure 7-9As can be seen in the figure, the test interval is 10 mHZ-100 kHZ, showing the battery impedance values of 225, 350 and 300 Ω;
[0112] 8. Using AP(AN-VAC)1 membrane, PAN membrane and P(AN-VAC) membrane as electrolyte, lithium sheet as negative electrode and lithium iron phosphate coating as positive electrode to assemble half-cell, the half-cell rate performance test was then carried out. The charge and discharge cycles were carried out at current densities of 0.2 C, 0.5 C, 1 C, 2 C, 3 C and 0.2 C respectively. The cut-off voltage of the test was 2.5-4.2 V. The charge and discharge cycles were carried out 5 times at each rate. The results are as follows Figure 10-12 shown.
[0113] from Figure 10-12 As can be seen, the half-cell can be stably charged and discharged at various current densities, with similar specific capacities at the beginning and the end when returning to 0.2 C, demonstrating the stable electrochemical properties of AP(AN-VAC)1. At the maximum current density of 3C, the specific capacity reaches 123.9 mAh / g; whereas the specific capacities of PAN and P(AN-VAC) fluctuate significantly with current density. Overall, this demonstrates that AP(AN-VAC)1 has an excellent range of applicable current densities.
[0114] Experimental detection of Example 2 and Comparative Examples 1 and 2:
[0115] A half-cell was assembled using AP(AN-VAC)2 membrane, PAN membrane and P(AN-VAC) membrane as electrolyte, lithium sheet as negative electrode and lithium iron phosphate coating as positive electrode. The half-cell rate performance test was then carried out. The charge and discharge cycles were carried out at current densities of 0.2 C, 0.5 C, 1 C, 2 C, 3 C and 0.2 C respectively. The cut-off voltage of the test was 2.5-4.2 V. Five charge and discharge cycles were carried out at each rate. The results are shown in the figure below. Figure 11-13 shown.
[0116] from Figure 11-13 As can be seen, the half-cell can charge and discharge stably at various current densities, with similar specific capacities at the beginning and end of the charge cycle returning to 0.2 C, demonstrating the electrochemical stability of AP(AN-VAC)2. At the maximum current density of 3C, the specific capacity reaches 102 mAh / g; in contrast, the specific capacities of PAN and P(AN-VAC) fluctuate significantly with current density. Overall, AP(AN-VAC)2 demonstrates an excellent current density range. However, its specific capacity retention is not as good as that of AP(AN-VAC)1.
[0117] Experimental detection of Example 3 and Comparative Examples 1 and 2:
[0118] A half-cell was assembled using AP(AN-VAC)5 membrane, PAN membrane and P(AN-VAC) membrane as electrolyte, lithium sheet as negative electrode and lithium iron phosphate coating as positive electrode. The half-cell rate performance test was then carried out. The charge and discharge cycles were carried out at current densities of 0.2 C, 0.5 C, 1 C, 2 C, 3 C and 0.2 C respectively. The cut-off voltage of the test was 2.5-4.2 V. Five charge and discharge cycles were carried out at each rate. The results are shown in the figure below. Figure 11 ,12,14 as shown.
[0119] from Figure 11 ,12,14 It can be seen that the half-cell can be stably charged and discharged at different current densities, with similar specific capacity values at the beginning and the end when returning to 0.2 C, indicating that the electrochemical properties of AP(AN-VAC)5 are stable. At the maximum current density of 3C, the specific capacity reaches 101.3 mAh / g; while the specific capacity of PAN and P(AN-VAC) fluctuates greatly with changes in current density, their specific capacity retention is not as good as that of AP(AN-VAC)1.
[0120] Experimental detection of Example 4 and Comparative Examples 1 and 2:
[0121] A half-cell was assembled using AP(AN-VAC)9 membrane, PAN membrane and P(AN-VAC) membrane as electrolyte, lithium sheet as negative electrode and lithium iron phosphate coating as positive electrode. The half-cell rate performance test was then carried out. The charge and discharge cycles were carried out at current densities of 0.2 C, 0.5 C, 1 C, 2 C, 3 C and 0.2 C respectively. The cut-off voltage of the test was 2.5-4.2 V. Five charge and discharge cycles were carried out at each rate. The results are shown in the figure below. Figure 11 ,12,15 as shown.
[0122] from Figure 11 ,12,15 It can be seen that the half-cell can be stably charged and discharged at different current densities, with similar specific capacity values at the beginning and the end when returning to 0.2 C, indicating that the electrochemical properties of AP(AN-VAC)9 are stable. At the maximum current density of 3C, the specific capacity reaches 76.5 mAh / g; while the specific capacity of PAN and P(AN-VAC) fluctuates greatly with changes in current density; however, their specific capacity retention rate is not as good as that of AP(AN-VAC)1.
[0123] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions and improvements made within the spirit and principles of the present invention should be included in the scope of protection of the present invention.
Claims
1. A method for preparing a flame-retardant polymer electrolyte for lithium-ion batteries, characterized in that: The steps of the preparation method are as follows: (1) Acrylonitrile and vinyl acetate are dissolved in deionized water to obtain solution A, and sodium lauryl sulfate and potassium persulfate are added to the solution A under a nitrogen atmosphere to obtain solution B. The specific process corresponding to each 9 g of acrylonitrile is as follows: 9 g of acrylonitrile and 1 g of vinyl acetate are dissolved in 30 mL of deionized water to obtain solution A; 0.2 g of sodium lauryl sulfate and 0.3 g of potassium persulfate are slowly added to the solution A under nitrogen conditions to obtain a homogeneous solution B; (2) soaking the solution B in a diethylenetriamine solution to obtain a solution C, specifically comprising the following steps: soaking the homogeneous solution B in 40 mL of a diethylenetriamine solution under a nitrogen atmosphere to obtain a solution C; (3) The solution C is filtered, washed, and dried to obtain product D. The specific steps are: after filtering the solution C, washing it with deionized water and ethanol in sequence to obtain a white solid product; heating and drying the white solid product to obtain product D, the heating temperature is 60°C; (4) adding the product D to bacterial cellulose and lithium bis(trifluoromethanesulfonyl)imide, and dissolving the mixture in N-methylpyrrolidone to obtain a solution E. The specific steps are as follows: mixing 1 g of the product D, 3 g of bacterial cellulose having a mass concentration of 0.4%, and 0.3 g of lithium bis(trifluoromethanesulfonyl)imide, and dissolving the mixture in 15 ml of N-methylpyrrolidone to obtain a solution E; (5) pouring the solution E into a mold, heating and evaporating the solvent to obtain a flame retardant polymer electrolyte AP (AN-VAC), wherein the specific steps are pouring the solution E into a polytetrafluoroethylene template, heating at 60°C for 6 h, and obtaining a flame retardant polymer electrolyte AP (AN-VAC); In the step (1), the concentration of acrylonitrile is 95% w / v, and the concentration of vinyl acetate is 95% w / v; in the step (2), the concentration of N-methylpyrrolidone is 95% w / v.
2. A flame retardant polymer electrolyte for lithium ion batteries, characterized in that: The flame-retardant polymer electrolyte is prepared by the preparation method according to claim 1.
3. A method for preparing a flame-retardant polymer electrolyte lithium-ion battery, characterized in that: The lithium-ion battery includes a lithium half-cell or a lithium full-cell, The lithium half-cell preparation method comprises the following steps: (A) Lithium iron phosphate: carbon black: polyvinylidene fluoride was dispersed in N-methylpyrrolidone in a ratio of 8:1:1, ground evenly, and then coated on aluminum foil with a scraper and dried to obtain a lithium iron phosphate electrode; (B) A lithium battery was prepared using a metal lithium sheet as the negative electrode, a lithium iron phosphate sheet as the positive electrode, and AP (AN-VAC) as a polymer flame retardant electrolyte. The lithium full battery preparation method comprises the following steps: (a) Lithium iron phosphate: carbon black: polyvinylidene fluoride was dispersed in N-methylpyrrolidone in a ratio of 8:1:1, ground evenly, and then coated on aluminum foil with a scraper and dried to obtain a lithium iron phosphate electrode; (b) artificial graphite: carbon black: polyvinylidene fluoride was dispersed in N-methylpyrrolidone in a ratio of 8:1:1, ground evenly, and then coated on aluminum foil using a scraper and dried to obtain a graphite electrode; (c) A lithium battery was prepared using graphite as the negative electrode, lithium iron phosphate as the positive electrode, and AP (AN-VAC) as the polymer flame retardant electrolyte. The AP (AN-VAC) is prepared by the preparation method according to claim 1.
4. A flame retardant polymer electrolyte lithium ion battery, characterized in that: The lithium-ion battery is prepared by the preparation method according to claim 3.